Commutating rotary transformer

ABSTRACT

Commutating rotary transformer having a primary section which rotates with the head assembly and a stationary secondary section which is mounted adjacent to the primary section. The primary section has a plurality of arcuately disposed windings wound on radially extending magnetic core segments, the number of windings and core segments corresponding to the number of heads. The secondary section has an arcuately disposed winding wound on a radially extending magnetic core segment which is disposed to be aligned successively with different ones of the primary core segments as the primary section rotates, whereby the signals from different ones of the rotating transducer heads are successively coupled to the stationary secondary winding.

United States Patent [191 Hibbard COMMUTATING ROTARY TRANSFORMER Earl Roger l-libbard, Santa Clara, Calif.

[73] Assignees American Videonetics Corporation, Sunnyvale, Calif.

22 Filed: Mar. 25, 1974 21 Appl. No.: 454,257

[75] Inventor:

[451 Oct. 7, 1975 Primary ExaminerVincent P. Canney Attorney, Agent, or FirmFlehr, Hohbach, Test, Albritton & Herbert [57] ABSTRACT Commutating rotary transformer having a primary section which rotates with the head assembly and a stationary secondary section which is mounted adjacent to the primary section. The primary section has a plurality of arcuately disposed windings Wound on radially extending magnetic core segments, the number of windings and core segments corresponding to the number of heads. The secondary section has an arcuately disposed winding wound on a radially extending magnetic core segment which is disposed to be aligned successively with different ones of the primary core segments as the primary section rotates, whereby the signals from different ones of the rotating transducer heads are successively coupled to the stationary secondary winding.

8 Claims, 4 Drawing Figures U.S. Patent Oct. 7,1975 3,911 486 SWITCHER PLAY BACK COMMUTATING ROTARY TRANSFORIVIER BACKGROUND OF THE INVENTION This invention pertains generally to apparatus for making electrical connections with circuits carried by a rotative member and more particularly to a commutating rotary transformer for successively delivering signals to or from the heads of a transverse scan tape recorder.

A transverse scanning recorder of the prior art, commonly known as a quadraplex recorder, has four transducer heads spaced in quadrature about an axis extending in a direction generally parallel to the direction of tape travel. As the tape moves past the rotating head assembly, it is scanned successively by the four heads along paths lying generally perpendicular to the direction of tape travel.

Heretofore, connections have been made between the fixed circuitry and the rotating heads of a transverse scan recorder by means of slip rings and rotary transformers. Slip rings are subject to well known disadvantages such as mechanical contact and wear, and they are delicate and expensive to manufacture.

In the rotary transformers of the prior art, a separate transformer is provided for each of the four channels. Each transformer has a primary winding and a secondary winding, and the windings are disposed side-by-side along the axis of rotation, with the primary windings constrained for rotation with the head assembly and the secondary windings stationary. With these transformers, coupling with all four heads is continuous, and commutation of the output signals during the playback process is accomplished by a four channel switcher. This switcher is a complicated network which delivers the signals from different ones of the heads in a predetermined order, and it is generally necessary to amplify the signals from the transformer secondaries before they are applied to the switcher. This requires a separate preamplifier for each of the channels.

SUMMARY AND OBJECTS OF THE INVENTION In the commutating rotary transformer of the invention, only the active heads are coupled at any given time. The transformer includes a primary section which rotates with the head assembly and a stationary secondary section which is mounted adjacent to the primary section. The primary section has a plurality of arcuately disposed windings wound on radially extending magnetic core segments, the number of windings and core segments corresponding to the number of heads. The secondary section has an arcuately disposed winding wound on a radially extending magnetic core segment which is disposed to be aligned successively with different ones of the primary core segments as the primary section rotates, whereby the signals from different ones of the rotating transducer heads are successively coupled to the stationary secondary winding. In a preferred embodiment, the primary windings are arranged in two groups disposed along concentric circular paths of different radii, and the secondary includes two radially extending magnetic core segments with an arcuately disposed winding on each, with each of the secondary windings being disposed to be coupled with the windings in only one of the two primary groups. The secondary windings are arranged to provide a slight overlap at the beginning and end of each scan, and switching be tween the secondary windings is provided by a simple two channel switcher.

It is in general an object of the invention to provide a new and improved commutating rotary transformer.

Another object of the invention is to provide a commutating rotary transformer of the above character which is particularly suitable for use in a transverse scan tape recorder.

Additional objects and features of the invention will be apparent from the following description in which the preferred embodiment is set forth in detail in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of the primary section of a commutating rotary transformer according to the invention.

FIG. 2 is an elevational view of the secondary section of a commutating rotary transformer according to the invention.

FIG. 3 is a sectional view of the assembled transformer, taken along lines 33 in FIGS. 1 and 2.

FIG. 4 is a block diagram illustrating the use of the transformer of FIGS. l3 in a transverse scan tape recorder.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIGS. 1 and 4, the invention is illustrated in connection with the rotating head assembly of a transverse scan recorder having eight circumferentially spaced heads designated Hl-HS. The heads are positioned for scanning a magnetic tape T in a direction generally perpendicular to the direction normal to the plane of the page, and in the vicinity of the head assembly the tape is bowed transversely by a suitable guide, not shown. The spacing between adjacent heads is made less than the width of the tape to provide a few degrees of overlap at the end of one scan and the beginning of the next.

The commutating rotary transformer comprises a primary section 10 and a secondary section II. The primary section includes a cup-shaped base 16, and it is affixed to the head assembly and constrained for rotation therewith by a screw 17. A plurality of radially extending magnetic core segments 21-28 are mounted on base 16 and arranged in an inner group consisting of the odd numbered segments. The core segments are generally sector shaped, and the segments in the inner group are spaced in quadrature about a central core section 29. The outer segments are interposed between the inner segments, and they are separated from the inner segments and the central core section by air gaps 31 and 32. Base 16 is preferably fabricated of a nonmagnetic material such as aluminum, and the core segments are fabricated of a ferrite material such as Ferroxcube 4C4. Alternatively, if desired, aluminum or another non-magnetic material can be utilized in place of air gaps 31 and 32 between the inner and outer core segments.

Primary windings P1P8 are wound on core segments 21-28 and disposed in arcuately extending slots in the segments. In a preferred transformer for a frequency range on the order of 0.5 to 6.5 MHz, each primary winding consists of seven turns of No. 47 copper wire. The even numbered windings, i.e. the windings on the inner group of core segments, are disposed along a circular path having a radius less than the inner radius of the outer core segments. The odd numbered windings are disposed along a circular path which has a radius greater than the outer radius of the inner core segments.

Connections to the primary windings are made by leads passing through openings 36 in base 16 to a printed circuit board 37 which is mounted in a recessed area at the rear of the base. Connector pins 38 on the circuit board mate with sockets on the head assembly, and connections between the winding leads and the connector pins are made by conductive foil on the circuit board. In the preferred embodiment, the odd numbered heads are connected to the windings adjacent to them, and the even numbered heads are connected to the diametrically opposed windings. Thus, head H1 is connected to the adjacent winding Pl, head H2 is connected to the opposed winding P2, and so on.

The secondary section 11 of the transformer includes a cup-shaped base 41 which is preferably fabricated of a nonmagnetic material such as aluminum. A hollow threaded stud 42 extends axially from the rear of the base to provide means for mounting the secondary section. Magnetic core sections 51 and 52 are mounted on the front of base 41. Segments 51 and 52 are generally sector-shaped, and they are fabricated of a high frequency ferrite material such as Ferroxcube 4C4.

Secondary windings S1 and S2 are wound on segments 51 and 52 and disposed in arcuately extending slots in the segments. Winding S1 is disposed along a circular path having a radius corresponding to the radius of the outer group of primary windings, and winding S2 is disposed along a circular path having a radius corresponding to the inner group of primary windings. In the preferred embodiment for a frequency range on the order of 0.5 to 6.5 MHz, each of the secondary windings have seven turns of No. 47 copper wire. Leads from the windings pass through openings 54 in base 41 to a printed circuit board 56 which is mounted in the rear of the base. Conductive foil leads on the circuit board provide connections between the winding leads and conductors leading to the circuitry with which the transformer is used.

When the transformer is assembled, illustrated in FIG. 3, the primary and secondary sections are disposed coaxially of the head assembly, with the axial faces of the core segments confronting each other. These faces are preferably lapped so that segments of the two sections can be in close proximity to minimize losses across the air gap between them. Secondary winding S1 is aligned with the odd numbered primary windings, and secondary winding S2 is aligned with the even numbered primary windings. The secondary core segments and windings are wider than the primary core segments and windings, and in the preferred embodi ment each of the primary windings has an arc length on the order of 45 and each of the secondary windings has an arc length on the order of 90.

As illustrated in FIG. 4, during the playback process secondary windings S1 and S2 are connected to the inputs of preamplifiers 61 and 62, respectively. The outputs of the preamplifiers are connected to a two channel switcher 63 of known design. The output of the switcher is connected to the playback circuitry 64 of the tape recorder. Switcher 63 operates in synchronization with the head assembly, alternately passing the signals from the two secondary windings to the playback circuitry. In a video recorder where each scan ofa head across the tape corresponds to a number of horizontal lines of the picture, for example 10 to 20 lines, switching occurs just before the horizontal sync pulse during the front porch interval for the first line of each scan.

Operation and use of the commutating rotary transformer can be described briefly. The primary section is mounted coaxially of the rotating head assembly of a transverse scanning recorder and constrained for rotation therewith. The secondary section is mounted in a fixed position coaxially of the primary section with the core segments of the primary section in close axial proximity to the core segments of the secondary section. As the head assembly and primary section rotate, the secondary core segments are aligned with successive ones of the primary segments to provide coupling with successive ones of the primary windings.

With the primary and secondary sections positioned as shown in FIGS. 1-3, primary core segments 21 and 24 are aligned with secondary core segment 51, and primary segments 25 and 28 are aligned with secondary segment 52. Windings Pland S1 are coupled by core segments 21 and 51, and windings P8 and S2 are coupled by segments 28 and 52. None of the other primary windings are coupled to the secondary windings. In this regard, it can be noted that even though core segments 24 and 51 are aligned, there is no coupling between primary winding P4 and secondary winding S1 because these windings lie on different radii. Likewise, there is no coupling between windings P5 and S2 because they also lie on different radii.

As the primary section rotates in the direction indicated by arrow 66 in FIG. 1, head H1 scans across tape T, and the output signal from this head is delivered to the playback circuitry by windings P1 and S1 and switcher 63. As head H1 approaches the end of its scan, head H2 begins to scan the tape. While head H2 scans the tape, primary core segment 22 is aligned with secondary segment 52, and primary winding P2, which is connected to head H2, is coupled to secondary winding S2. During this scan, the switcher delivers the signal from secondary winding S2 to the playback circuitry. As the head assembly rotates, the process continues, and the output signals from the different heads are delivered to the playback circuitry in the desired sequence.

Since each head begins its scan slightly before the proceeding head has completed its scan, there is a slight overlap in the signals delivered to the secondary windings for successive portions of the picture. This overlap is eliminated by the switcher and is not visible in the picture. The switching occurs during the retrace interval between lines, and there is no loss of picture information during it.

During the recording process, the record signal is fed.

in parallel to secondary windings S1 and S2. The record signal is coupled to the odd numbered and even numbered heads as they scan the tape in sequence. No external signal switching is performed during the record process, hence each head records a path on the tape which extends more than 45 in arc length. The redundant recording at the beginning and end of each scan provides the overlap for the playback process.

It is apparent from the foregoing that a new and improved commutating rotary transformer has been provided. While only the presently preferred embodiment has been described, as will be apparent to those familiar with the art, certain changes and modifications can be made without departing from the scope of the invention as defined by the following claims.

I claim:

1. A commutating rotary transformer for successively coupling signals to or from a plurality of rotating transducer heads in a tape recorder, said transformer comprising: a primary section constrained for rotation about an axis with the transducer heads, said primary section having a plurality of radially extending magnetic core segments and an arcuately disposed primary winding on each of the core segments, each primary winding being connected to a different one of the transducer heads, and a stationary secondary section comprising a radially extending magnetic core segment and an arcuately disposed winding on the core segment, the secondary section being disposed coaxially of the primary section and spaced axially therefrom with the secondary core segment in close proximity to the primary core segments and positioned to be aligned successively with different ones of the primary segments as the primary section rotates, whereby different ones of the rotating transducer heads are successively coupled to the stationary secondary winding.

2. A commutating rotary transformer for coupling electrical signals with a plurality of circuits carried by a rotative member, said transformer comprising: a first section disposed coaxially of the rotative member and constrained for rotation therewith, said first section having a plurality of radially extending magnetic core segments and a plurality of spaced apart arcuately disposed windings wound on the core segments, said windings being connected to the circuits carried by the rotative member, and a second section comprising a radially extending magnetic core segment and an arcuately disposed winding wound on the core segment, said sec ond section being disposed coaxially of the first section and spaced axially therefrom with the core segment of the second section in close proximity to the core segments of the first section, the core segment of the sec ond section being aligned successively with different ones of the core segments of the first section as said first section rotates whereby the winding on the second section is coupled successively to the windings on the first section.

3. The commutating rotary transformer of claim 2 wherein the windings of the first section are disposed along a circular path of predetermined radius centered about the axis of rotation and the winding of the second section is disposed on an arcuate path of the predetermined radius.

4. A commutating rotary transformer for successively coupling signals to or from a plurality of rotating transducer heads in a tape recorder, said transformer comprising: a primary section constrained for rotation about an axis with the transducer heads, said primary section having a plurality of radially extending mag netic core segments and an arcuately disposed primary winding on each of the core segments, each primary winding being connected to a different one of the transducer heads, and a stationary secondary section comprising a radially extending magnetic core segment and an arcuately disposed winding on the core segment, the primary windings being arranged in two groups disposed respectively along circular paths of first and second predetermined radii centered about the axis of rotation and the secondary section having two radially extending magnetic core segments and an arcuately disposed winding on each of said segments, the secondary windings being spaced from the axis of rotation by distances corresponding respectively to the first and second radii, the secondary section being disposed coaxially of the primary section and spaced axially therefrom with the secondary core segment in close proximity to the primary core segments and positioned to be aligned successively with different ones of the primary segments as the primary section rotates, whereby different ones of the rotating transducer heads are successively coupled to the stationary secondary winding.

5. The commutating rotary transformer of claim 4 wherein adjacent ones of the transducer heads are connected to primary windings in different ones of the two groups.

6. The commutating rotary transformer of claim 4 to gether with switching means for selectively applying the signals from the secondary windings to a signal processing circuit.

7. A commutating rotary transformer for coupling electrical signals with a plurality of circuits carried by a rotative member, said transformer comprising: a first section disposed coaxially of the rotative member and constrained for rotation therewith, said first section having a plurality of radially extending magnetic core segments and a plurality of spaced apart arcuately disposed windings wound on the core segments, said windings being connected to the circuits carried by the rotative member, and a second section comprising a radially extending magnetic core segment and an arcuately disposed winding wound on the core segment, the windings of the first section being arranged in two groups disposed respectively along circular paths of first and second predetermined radii centered about the axis of rotation and the second section having two radially extending magnetic core segments and two windings disposed respectively on arcuate paths of said first and second radii, the second section being disposed coaxially of the first section and spaced axially therefrom with the core segment of the second section in close proximity to the core segments of the first section, the core segment of the second section being aligned successively with different ones of the core segments of the first section as said first section rotates, whereby the winding on the second section is coupled successively to the windings on the first section.

8. The commutating rotary transformer of claim 7 together with electronic switching means for selectively connecting the windings of the second section to a sig- 

1. A commutating rotary transformer for successively coupling signals to or from a plurality of rotating transducer heads in a tape recorder, said transformer comprising: a primary section constrained for rotation about an axis with the transducer heads, said primary section having a plurality of radially extending magnetic core segments and an arcuately disposed primary winding on each of the core segments, each primary winding being connected to a different one of the transducer heads, and a stationary secondary section comprising a radially extending magnetic core segment and an arcuately disposed winding on the core segment, the secondary section being disposed coaxially of the primary section and spaced axially therefrom with the secondary core segment in close proximity to the primary core segments and positioned to be aligned successively with different ones of the primary segments as the primary section rotates, whereby different ones of the rotating transducer heads are successively coupled to the stationary secondary winding.
 2. A commutating rotary transformer for couPling electrical signals with a plurality of circuits carried by a rotative member, said transformer comprising: a first section disposed coaxially of the rotative member and constrained for rotation therewith, said first section having a plurality of radially extending magnetic core segments and a plurality of spaced apart arcuately disposed windings wound on the core segments, said windings being connected to the circuits carried by the rotative member, and a second section comprising a radially extending magnetic core segment and an arcuately disposed winding wound on the core segment, said second section being disposed coaxially of the first section and spaced axially therefrom with the core segment of the second section in close proximity to the core segments of the first section, the core segment of the second section being aligned successively with different ones of the core segments of the first section as said first section rotates whereby the winding on the second section is coupled successively to the windings on the first section.
 3. The commutating rotary transformer of claim 2 wherein the windings of the first section are disposed along a circular path of predetermined radius centered about the axis of rotation and the winding of the second section is disposed on an arcuate path of the predetermined radius.
 4. A commutating rotary transformer for successively coupling signals to or from a plurality of rotating transducer heads in a tape recorder, said transformer comprising: a primary section constrained for rotation about an axis with the transducer heads, said primary section having a plurality of radially extending magnetic core segments and an arcuately disposed primary winding on each of the core segments, each primary winding being connected to a different one of the transducer heads, and a stationary secondary section comprising a radially extending magnetic core segment and an arcuately disposed winding on the core segment, the primary windings being arranged in two groups disposed respectively along circular paths of first and second predetermined radii centered about the axis of rotation and the secondary section having two radially extending magnetic core segments and an arcuately disposed winding on each of said segments, the secondary windings being spaced from the axis of rotation by distances corresponding respectively to the first and second radii, the secondary section being disposed coaxially of the primary section and spaced axially therefrom with the secondary core segment in close proximity to the primary core segments and positioned to be aligned successively with different ones of the primary segments as the primary section rotates, whereby different ones of the rotating transducer heads are successively coupled to the stationary secondary winding.
 5. The commutating rotary transformer of claim 4 wherein adjacent ones of the transducer heads are connected to primary windings in different ones of the two groups.
 6. The commutating rotary transformer of claim 4 together with switching means for selectively applying the signals from the secondary windings to a signal processing circuit.
 7. A commutating rotary transformer for coupling electrical signals with a plurality of circuits carried by a rotative member, said transformer comprising: a first section disposed coaxially of the rotative member and constrained for rotation therewith, said first section having a plurality of radially extending magnetic core segments and a plurality of spaced apart arcuately disposed windings wound on the core segments, said windings being connected to the circuits carried by the rotative member, and a second section comprising a radially extending magnetic core segment and an arcuately disposed winding wound on the core segment, the windings of the first section being arranged in two groups disposed respectively along circular paths of first and second predetermined radii centered about the axis of rotation and the second section having two rAdially extending magnetic core segments and two windings disposed respectively on arcuate paths of said first and second radii, the second section being disposed coaxially of the first section and spaced axially therefrom with the core segment of the second section in close proximity to the core segments of the first section, the core segment of the second section being aligned successively with different ones of the core segments of the first section as said first section rotates, whereby the winding on the second section is coupled successively to the windings on the first section.
 8. The commutating rotary transformer of claim 7 together with electronic switching means for selectively connecting the windings of the second section to a signal processing circuit. 